ouster



(No Model.) 2 Sheets-Sheet 1.

J. S. CUSTER.

AIR BRAKB.

No. 553,481. Patented Jan. 21,1896.

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W'TNESSES: oawifl. ,m@

ANDREW 8.6RANAMJHOTOUTHOVWASNINGI'DNDC.

UNITED STATES PATENT OFFICE.

JOHN S. OUSTER, OF PITTSBURG, PENNSYLVANIA, ASSIGNOR TO THE \VEST- INGI-IOUSE AIR BRAKE COMPANY, OF SAME PLACE.

A lR-BRAKE.

SPECIFICATION forming part of Letters Patent No. 553,481, dated January 21, 1896;

Application filed May 25, 1894.

' To all whom it may concern.-

Be it known that I, JOHN S. CUSTER, a citizen of the United States, residing at Pittsburg, in the county of Allegheny and State of Pennsylvania, have invented or discovered a certain new and useful Improvement in Air- Brakes, of which improvement the following is a specification. A

The object of my invention is to provide an improvement in automatic fluid-pressure brake apparatus; and to this end it consists of means for controlling the exhaust of fluid under pressure from the brake-cylinder, preventing such exhaust when the auxiliary-reservoir pressure is reduced below a certain predetermined degree and permitting the restoration of auxiliary-reservoir pressure to a predetermined degree without releasing the brakes.

The improvement claimed is hereinafter fully set forth.

In the accompanying drawings, Figure 1 is a side elevation of a portion of an automatic fluid-pressure brake system with my improvement applied thereto, and Fig. 2 a central longitudinal section through the pressure-retaining valve device of my improvement.

The construction and relation of the trainpipe 1, branch pipe 2, triple valve 3, auxiliary reservoir 4, and brake-cylinder 5 (shown in Fig. 1.) are the same as employed in the Westinghouse system of air-brakes; but my invention is not limited in its application to that or any other specific system, as it may be employed in connection with any automatic fluid-pressure brake system of which an auxiliary reservoir and a triple-valve device form part, and the particular form of the triplevalve device is immaterial.

In the embodiment of my invention shown in the drawings the usual exhaust-port 6 of the triple-valve device 3 is connected by means of a pipe or passage '7 with an exhaustcontrolling valve device. (Shown in section in Fig. 2.) One end of the pipe ,7 opens into a passage or chamber 8, which normally is in communication with the atmosphere through 'the passages 9, 10, and 11; but in Fig. 2 this communication is shown closed by the valve 12 in the passage 9. The valve 12 is con- Serial No. 512,430. (No model.)

nected, by means of a stem 13, with a movable abutment or piston 14 in a chamber 15, and the piston or movable abutment 14 is subject on one side to the pressure of a spring 16 tending to move it in one direction, and on the other side to the pressure in the auxiliary reservoir 4 tending to move it in the opposite direction.

The chamber 15 is at all times in communication with the auxiliary reservoir 4 through the pipe or passage 17, and the area of the piston 14 and the resistance of the spring 16 are so proportioned that when the normal inclosed by the circular projection 19 on the spring side of the piston, and is so proportioned that the auxiliary-reservoir pressure acting thereon is sufficient to compress the spring 16 and hold the piston against the seat 18 so long as the auxiliary-reservoir pressure equals or exceeds a certain predetermined am ountsay fifty pounds to the square inch.

\Vhen the auxiliary-reservoir pressure is reduced below this limit the resistance of the spring 16 moves the piston away from the seat 18 and forces it against the seat 20, a

circular rib or projection 21 being formed on the reservoir side of the piston and adapted to bear on the seat 20, so as to form a tight joint. The area inclosed by the circular rib or projection 21 determines the efiective area of the piston when it is held against the seat 20, and this area is less than the effective area of the piston when it bears on the seat 18, so that a greater pressure per square inch in the auxiliary reservoir will be necessary to move the piston away from the seat 20 than is necessary to hold it against the seat 18. It will be seen that the piston 14 is in effect a differential piston, and that the circular ribs or projections 19 and 21 act as valves to prevent the escape of fluid from the auxiliary reservoir.

condition The seats 18 and 2O,Whicl1 maybe made of rubber, leather, or other suitable material, are fitted, respectively, in the part 24 of the casing and in a removable bushing 22,which may be Withdrawn from the chamber for the purpose of examining or repairing the seat 20 When the parts 23 and 24 of the casin g are disconnected. A groove 25 in the bushing 22 forms a passage around the edge of the piston 14 when in the position shown in Fig. 2, which permits the escape of fluid under pressure from the upper side of the piston outside of the projection 21 to the chamber 26, and thence around the stem 13 to the passage 10 and port 11 to the atmosphere.

The spring 16 may be adjusted by means of the hollow screw-plug 28,Which has a head 29 adapted to be turned by a wrench when the part 27 is disconnected from the plug.

When the brake system is in its normal that is, with the train-pipe and auxiliary reservoir charged with fluid under a pressure of about seventy pounds per square inchand the brakes released, the piston 14 bears against the seat 18 and the valve 12 is open. The brake-cylinder is then in communication with the atmosphere through the exhaust-cavity in the slide-valve of the triple valve and the port or passage 6, pipe 7, and passages 8, 9, 10, and 11.

In applying the brakes by a reduction of train-pipe pressure the triple-valve device closes communication between the brake-cylinder and the pipe or passage 7 and opens communication between the brake-cylinder and the auxiliary reservoir, and fluid under pressure flows from the'auxiliary reservoir to the brake-cylinder and causes a reduction of the pressure in the auxiliary reservoir. When this reduction of pressure is small the piston 14 remains on the seat 18 and holds the valve 12 open, so that if it is desired to release the brakes by an increase in train-pipe pressure the movement of the triple valve, which connects the brake-cylinder with the pipe or passage 7, will be sufficient to exhaust the fluid under pressure from the brake-cylin der; but if the reduction of-auxiliary-reservoir pressure has been considerable-that is, be-

low the limit of pressure required to hold the piston 14 on the seat 18 against the resistance of the spring 16the spring will move the piston 14 and valve 12 into the positions shown in Fig. 2, the piston then bearing on the seat 20 and the valve 12 closing the port 9. If the triple-valve device be then moved by an increase of train-pipe pressure into position for charging the auxiliary reservoir, which is also the position for releasing the brakes, communication will be opened from the brake-cylinder to the pipe or passage 7; but exhaust to the atmosphere will be prevented by the valve 12 closing the port 9 and the auxiliary reservoir will be recharged with fluid under pressure from the train-pipe until the pressure in the auxiliary reservoir acting on the smaller area of the piston 14 is sufficient to overcome the resistance of the spring 16 and move the piston from the seat 20. As soon as the piston is moved from the seat 20 the auxiliaryreservoir pressure acts on the larger area of the piston and forces it against the seat 18, thereby opening the valve 12 and permitting the fluid under pressure in the brake-cylinder to escape to the atmosphere.

It will be seen that the valve 12 acts as a pressure-retaining valve 'for retaining fluid under pressure in the brake-cylinder While the auxiliary reservoir is being recharged, that it is automatic in its action and that its operation depends on variations of pressure in the auxiliary reservoir only, independent of the pressure in the train-pipe or brake-cylinder.

So long as the auxiliary-reservoir pressure is above a certain limit or is high enough to permit of a desirable increase of pressure in the brake-cylinder by a reduction of trainpipe pressure, the pressure-retainin g valve 12 remains open; but so soon as the auxiliaryreservoir pressure becomes reduced below that limit, or an increase in brake-cylinder pressure cannot be effected by a further reduction of train-pipe pressure, the pressureretaining valve closes and permits a restoration of pressure in the auxiliary reservoir, which may be utilized to further increase the brake-cylinder pressure Without releasing the brakes or to efl ect another application of the brakes.

I claim as my invention and desire to secure by Letters Patent In an automatic fluid pressure brake system, the combination, with an auxiliary reservoir and a brake cylinder, of a pressure retaining valve for preventing the exhaust of fluid under pressure from the brake cylinder, and a piston or movable abutment for operating the pressure retaining valve Which is exposed to auxiliary reservoir pressure and which presents different areas to the action of the auxiliary reservoir pressure in the open and closed positions of the retaining valve respectively, substantially as set forth.

In testimony whereof I have hereunto set my hand.

JOHN S. CUSTER.

Vitnesses:

'F. E. GAITHER, T. J HOGAN. 

